Fluid operated rowing machine



6, 1966 A. R. JOHNSON 3,266,801

FLUID-OPERATED ROWING MACHINE Filed Oct. 26, 1964 5 Sheets-Sheet 1 J?41/ ff 1% f7 14 1966 A. R. JOHNSON 3,266,801;

FLUID-OPERATED ROWING MACHINE Filed Oct. 26, 1.964 5 Sheets-Sheet 2 5 A.R JOHNSON 3,266,801

FLUID-OPERATED ROWING MACHINE Filed Oct. 26, 1964 5 Sheets-Sheet 3United States Patent 3,266,801 FLUKD OPERATED RGWING MAQHINE Avery R..lohnson, Boston, Mass, assignor to Rio- Dynamics Incorporated,Cambridge, Mass, a corporation of Massachusetts Filed (let. 26, 1964,Ser. No. 406,406 9 Claims. (Cl. 272-72) This invention relates to whatare called rowing m-achines, which are athletic exercise or practicedevices in the form of equipment with oars, used by .a person inimitating the actions of rowing a boat. More particularly the inventionrelates to a portable rowing machine that is used on dry land or in theabsence of water as distinguished from those that require a pool, tankor other body of water for their use.

Portable rowing machines of this general type are well known, butprevious devices fail to furnish certain action and reaction forcesencountered in the actual rowing of a boat in water and therefore do nottruly simulate the natural rowing effort and effect to a person usingthe machine.

The principal object of this invention therefore, is to provide a rowingmachine having action and reaction characteristics and forces closelyapproximating those found in manipulating the oars of a boat in water sothat use of the machine as an exerciser truly simulates the rowingeffort of a person in a rowboat and the effect of the moving water onthe ears.

Many prior rowing machines function strictly as exercising devices, suchdevices lacking any means for gauging the effort expended or the resultsaccomplished in using them. Another object of the present invention isto provide, in a portable rowing machine of the type here involved,means including indicators to show the amount and direction of forcebeing exerted by the operator and the speed and/or distance attained byhim when using the device. In this way the machine may be used tomeasure and compare the effectiveness of a single operator at ditferenttimes, or as a competitive device to measure and judge the superiorityof one contestant over another when using the machine.

The principal object of the invention is met by providing a rowingmachine with cars, the movements of which are reflected by hydraulicpiston elements acting at the ends of the loops of a symmetrical closeddouble loop fluidfilled hydraulic system, this system having at itscenter, common to both loops, a fluid nrotonpump device that drives aflywheel. Operation of the piston elements by a stroke of the oarsstarts circulation of hydraulic fluid in both loops of the system andthrough the centrally located motor device to drive the flywheel. Theinertia of the rotating flywheel causes the motor-pump device to act asa pump and continue circulation of the fluid in 'both loops of thehydraulic system, applying pressure against the reverse sides of thepiston elements. Thus, after a stroke of the cars, fluid pressure willbe [brought to bear on the oars much as it would be in the case of anoar stroke in water, assuming that the handles of the oars are notdepressed at the end of the stroke. A valved bypass is provided in thesystem for'each car so that when the hand grip of the car is depressed,as it would be naturally at the end of the stroke to lift the car out ofthe water, the valve in the bypass is opened, pressure of circulatingfluid will not reach the piston element and the circulating hydraulicfluid will not influence the actuation of the oar. :By this means, thenatural reaction of an car to water at the end of a stroke is preserved.Other valving means are provided for this bypass to open the same andrelieve the piston element from the pressure of circulating fluid whenthe oar is twisted to a blade feathering position, and this valve icemay be the same one that is opened upon depression of the hand grips ofthe oars.

The circulating hydraulic system and the motor-pump with flywheelcharacteristic of this invention include components uniquely adapted forthe attachment of instruments for the measurement of force, balance ordirection, accumulated travel or distance, and speed According toanother aspect of this invention, performance measuring devices forindicating the force exerted land the direction or balance of pullbetween the cars are provided by hydraulically actuated instrumentslocated in a common fluid line bypassing the motor-pump and connected tocorresponding points in the two closed loops of the system. Instrumentsfor indicating distance and speed are of mechanical types, driven by arotating element on the motorapump, for example, by the flywheel.

Other objects and further details of that which is believed to be noveland included in this invention will be clear from the followingdescription and claims, taken with the accompanying drawing in which isillustrated an example of rowing machine embodying the present inventionand incorporating the motor-pump with flywheel at the center of thesymmetrical closed double loop hydraulic system and the performancemeasuring instruments as above generally described.

In the drawing:

FIG. 1 is a top plan view of a rowing machine according to the inventionshowing the general organization of parts;

FIG. 2 is a left-side elevational view of the same;

FIG. 3 is a vertical transverse view through one side of the machinesubstantially on the line and in the direction of the arrows 3-3 of FIG.1;

FIG. 4 is an enlarged vertical transverse section through one of thepiston chamber elements of the machine, substantially on the line and inthe direction of the arrows 4--4 of FIG. 2;

FIG. 5 is a vertical sectional view at right angles to FIG. 4substantially on the line 55 thereof;

FIG. 6 is a horizontal sectional view on the line 6--6 of FIG. 5;

FIG. 7 is an enlarged vertical longitudinal section, sub stantially onthe line and in the direction of the arrows 77 of FIG. 1, and

FIG. 8 is a diagrammatic view of the hydraulic system and principalassociated elements of apparatus according to this invention.

In the embodiment of the invention here shown, there is a tubular metalsupporting frame or base 10, having legs 11 and carrying foot rests 12.A seat 14 carrying rollers 16 is mounted to ride in tracks 18 secured tothe frame. Su-ch things are common in rowing machines and need not bedescribed in detail. Oars of a usual type 20 also are provided, but themounting and connecting of these cars in the apparatus constitutes adeparture from prior practices that is germane to the present invention.Because both sides of the machine are identical, although in reversepositions, the same reference numerals will be used herein for the partson each side, with the addition of the letter L for left and R for rightwhenever parts on the left or on the right side of the machine aredistinguished from one another.

Accordingly, the outer end of each car is supported generally from theframe or base as by an outrigger 22 which is fastened to a centralauxiliary frame 24 carried between the sides of the main frame in anysuitable fashion. Cross struts 26 and uprights 28, attached to eachother and to the auxiliary frame and Outriggers, provide a stableanchorage for an oar mount supporting plate 30 on each side of themachine, outboard of the central main and auxiliary frames. The carmount plates 30 may be ad justably secured on the uprights 28 and fixedat a desired level as by the clamping bars 32 or something similar. Theends of the legs and of the Outriggers may be provided with cushionedfriction tips, as shown, to prevent the machine from sliding on ormarring the floor when in use.

Supported by each of the oar mount plates is a piston receiving chamber34, shown here as of upright semicylindrical form, having a bottom wall35 suitably secured on the mounting plate, upright walls 36 and a topwall .37. Bolts 38 extending between the top and bottom walls may holdthese together against the upright walls, the entire chamber being madefluid-tight at its joints between the walls as by gaskets 39 or othersealing arrangements.

The piston element in each chamber is of the swinging blade or wingtype, pivoted vertically on an axis opposite the center of the straightupright wall portion of the piston chamber and having a cylindricalportion 40 with a flat rectangular blade or wing portion 42 extendingtherefrom into close sliding contact with the fiat top and bottom andcurved upright walls of the chamber. The top end of the cylindricalportion passes in rotatable sealed relation through the top chamber wall3 7, while the bottom of the piston is pivoted although sealed in thebottom wall 35. A sealing strip 44 is provided inside the piston chamberalongside the cylindrical portion 40 to seal one side of the piston fromthe other adjacent its pivot and furnish separate compartments in thechamber, variable in size depending upon the piston blade position.

An extension or collar 46 on the outside of the cylindrical portion ofthe piston carries an offset oar pivot bracket 48 with a horizontalpivot pin 50 offset outwardly of the vertical pivot axis of thecylindrical portion 40. The bracket 48 acts as a crank arm to swing thepiston blade 42 about the vertical axis of its cylindrical portion 40.The pivot pin 50 carries an oar lock simulating cylindrical socket 52with a central pivotal axis at right angles to the pivot pin 50, inwhich oar lock socket the outer end of an oar 20 is journaled in anysuitable fashion.

With the above arrangement, it will be seen that, as either oar isstroked or moved backward or forward from a given position the blade ofits piston will swing about a vertical axis through a correspondingangle and direction in the piston chamber, and the oar may be raised orlowered and twisted about its own axis in one direction or the otherduring this stroking of the oar or without stroking the oar. Thevertical pivot of the piston element allows the forward and backward oarmovement, the horizontal pivot pin allows the upward or downwardmovement and the axial pivot mounting of the oar in the socket 52permits rotation of the oar or twisting about its own axis. 'Forpurposes that will later appear, a readily visible mark or projection(not shown) is preferably pro vided on each oar to indicate its rotativeposition when the blade of the oar would be in proper vertical positionfor stroking or in horizontal position for feathering, as if the oar didhave a true blade. To conserve space, the oars of rowing machines arenot usually provided with true blades.

Means are provided whereby the action of the rowing machine is altereddepending upon the rotative position of the oar about its axis, or theraising and lowering of the inner end or hand grip of the oar, butbecause this involves the entire hydraulic system it will be explainedmore fully at a later point. However, it will be noted that at thecenter of the vertical axis of rotation of the piston blade there isslidably mounted a valve control rod 54 which extends through thecylindrical portion 40 of the piston and projects at its top end abovethe oar pivot bracket 48 and at its bottom end below the bottom wall 35of the piston chamber.

The hydraulic piping system characteristic of this invention is composedessentially of two identical closed loops symmetrically arranged andeach connected to a motor-pump 60 through a common central connection orinlet 56 and a common central connection or outlet 58. Connection 56leads to identical sections 62L and 62R of the hydraulic system oneither side of the machine. Each of these terminates at its outer end inan opening 64 in the piston chamber 34 in the compartment on one side ofthe piston blade 42. Completing the identical and symmetrical loops ofthe hydraulic system on either side of the machine, sections 66L and66R, equal in capacity to the sections 62, lead from the commonconnection 58 to openings 68L and 68R respectively in the piston chambercompartments on the opposite sides of the piston blades 42.

Ignoring the reaction controls of this invention for the moment, when anoperator pulls an oar 20 in a stroke, the corresponding piston blade 42will swing in the chamber 34 and produce pressure and flow of the liquidin the system through the opening 64 of the piston chamber, to thesection 62L or 62R of the system, and from the connection 56 into themotor-pump device 60. This will operate the device 60 as a motor anddrive the rotating shaft 70, on which a flywheel 72 is suitably secured.

The motor-pump 60 is a type of rotary fluid-pressure operated motordevice. Many such devices, when the motor is rotatably driven by anoutside force, will act in an opposite manner as a pump for the fluidcontained therein. One fluid motor-pump of this kind found particularlyuseful in the apparatus of the present invention is disclosed in UnitedStates Patent No. 2,821,171 issued January 28, 1958 to Lynn L. Charlson,reissued as No. Re. 25,291, December 4, 1962. Other fluid motor-pumps,such as one of the well known gear or turbine fluid pumps, might be usedwith this invention if it exhibits the desired reversible performancecharacteristics. In other words, the device must be capable ofperforming as a fluid-driven motor to drive the shaft 70 and flywheel 72when proper fluid pressure is applied at the hydraulic inlet 56.However, the device must also act in an opposite sense as a mechanicallydriven pump to produce fluid pressure in the hydraulic outlet 58 andflow of fluid when outside mechanical force rotates the shaft 70. Theinertia of rotating flywheel 72 provides the necessary outside drivingforce.

As the hydraulic fluid in the system passes through the motor, it leavesby the connection 58 and continues through the sections 66L and 66R ofthe loops on either side of the machine, passing therefrom through theopenings 68 of the piston chambers, thereby producing pressure in acompartment of the piston chambers against the reverse sides of thepiston blades 42. At the end of the stroke, if the operator does notmanipulate the oars properly, the inertia of the spinning flywheel willcause a continued fluid pressure in the system to tend to hold the oaron either side of the machine at its end-of-stroke position for as longas the flywheel rotates, the device 60 acting as a pump at this time, tokeep the fluid under pressure in the hydraulic system.

In order to provide a means whereby the oars may be returned by anoperator at the end of a stroke without the opposition of liquidpressure in the system, a return bypass 74 is provided on each side ofthe machine extending between the pipe sections 62 and 66 close to theopenings 64 and 68 in each chamber 34. Each return bypass in the systemis opened or closed by a valve 76, shown best in FIGS. 4 and 5, thedetails of which are not par ticularly important as long as the valvewill operate in the manner about to be described. In the formillustrated, the valve includes a spring (not shown) that tends to holdthe valve stem and valve 76 in a position so that bypass 74 is blocked.Outside of the valve body a pivoted crank arm 82 is mounted in suchposition that its forked end 84 extends under and in contact with thehead of the valve stem while the other end has a bearing surface 86extending under and in contact with the bottom end of the valve controlrod 54 previously mentioned. It

will be seen that when the rod 54 is depressed it lowers the end 86 ofthe crank arm 82 and raises the end 84, lifting the valve stem 80against the bias of the valve spring and opening valve 76 so that thebypass 74 is free for circulation of fluid directly from section 66 tosection 62, without the fluid applying pressure in the piston chamber34. When the inner ends or hand grips of the oars are properly loweredat the end of a stroke, this is the position of parts and the conditionof the hydraulic system desired, the device 68 operating as a pump topro duce circulation of hydraulic fluid from sections 66 to sections 62in the system under the influence of the spinning flywheel.

In order to control this bypass valve and actuate it as desired when theoar handle is properly manipulated by the operator, a valve control cam88 is provided on each oar at a position on the oar always locatedimmediately above the top end of the control rod 54. This cam is pro-Vided with outer surfaces for engagement with and depression of thevalve control rod whenever the hand grip of the oar is depressed beyonda certain point, as it would be when naturally making a return stroke inrowing, and raised surfaces on the cam are also arranged to depress thevalve control rod whenever an oar is twisted about its axis to anangular position in which the oar would be feathered.

Thus the action of the machine and the reaction forces produced willimitate closely those encountered in actual rowing. A stroke of the oarwhen its hand grip is raised and the oar is not feathered will startcirculation of fluid in the system, and this circulation will produceback pressure on the piston and on the oar until the inner end or handgrip is lowered or the oar is twisted to feathered position. A returnswing of the hand grip to starting position can then be made withoutresistance of the pressure of fluid circulating in the system. However,when the oars are again dipped, as by raising the hand grips, and a newstroke is started, the influence of the liquid moving in the system willbe felt on the blades of the pistons, imitating the reaction of movingwater that would be encountered by an oar in a boat when used in itsnatural environment. If an oar is not feathered, or if its handle is notproperly lowered as it should be on a return stroke, the liquid flowingin the system under the impetus of the spinning flywheel will oppose thereturn stroke of that oar much as moving water would oppose a return oarstroke under like conditions.

Note that if the motor-pump is of a reversible flow type, the machinewill work equally well in simulating back-paddling or reverse rowing. Inthis case the machine may be used not only as an exerciser but also as atraining device to familiarize a beginner with the proper way tomanipulate a pair of oars when handling a row boat. Maneuvering of aboat therefore may be learned on this machine by experience withoutgoing near a body of water.

A rowing machine with the action and reaction arrangements as abovedescribed lends itself peculiarly to the addition of applied forcemeasuring and performance accomplishment indicating instruments. Forexample, at identically spaced points on either side of the connection56 in the sections 62L and 62R of the hydraulic system, a bypass loop 90is connected, and in this loop a fluid pressure gauge 92 of conventionaldesign may be connected. This gauge, being open to the influence ofpressure from both sides of the system, will measure the net pressure orforce produced in the system by an opera.- tor during each stroke. Gauge92 may be calibrated in pounds per square inch. If the user of theequipment is pulling harder on one oar than on the other, this willproduce a greater pressure in one of the lines 62 than in the other, andthis difference in pressure between the two sides of the system may bemeasured and indicated by a differential flow indicating gauge 94 in thebypass loop 90, this instrument being conveniently calibrated in pointsof the compass if desired, to indicate the bearing of the operator usingthe machine. When these measurements are not deemed of importance, thebypass may be effectively closed off from the system by an appropriatehand valve 96.

Because the rotary shaft 70 of the motor-pump and the flywheel thereonare driven at rates directly proportional to movement of fluid in thehydraulic system, these rotating parts in turn may be used to driveinstruments for measuring other work being done by the machine.Accordingly, the flywheel may be provided with a driving belt or chain95 which extends around driving wheels or gears 97 and 98 for anodometer 99 and a tachometer 100 respectively which may indicatedistance and speed inappropriate nautical units.

As shown, each of the gauges or instruments 92, 94, 99 and 100 may besuitably mounted and supported in a housing 102 carried in the auxiliaryframe 24 in a position in front of the rower, so that he may observe hisperformance and vary his efforts in the manner he chooses. Themotor-pump 60 and flywheel also are conveniently supported and carriedin this housing so that the assembly may be maintained in a compactarea.

Although the connections 56 and 58 of the hydraulic system piping may bemade of rigid tubing, the major portions of sections 62 and '66 oneither side of the machine are' preferably of a flexible type, at leastup to the return bypass sections 74L and 74R. These sections, of course,should be rigid and mounted in a fixed position relative to the piStOnchambers so that the valve assemblies 76 therein are properly held infixed position for operation by the control rods 54.

Flexible tubing for the major portion of the hydraulic system also makesit possible to connect the out triggers to the sides of the auxiliaryframe in a pivotal fashion so that these sidewise extending members maybe folded upwardly toward one another. The auxiliary frame also may bedetachably secured to the main frame as by sliding bolt connections 104.When the main frame is disconnected and removed from the auxiliary frameand the outtriggers are folded over the auxiliary frame, casters 106 onthe housing 102 may be used to roll the auxiliary frame about from placeto place, the auxiliary frame with the collapsed outriggers serving as awheeled carrier for the detached main frame and other attachments. Withsuch arrangements the machine will occupy but a small area when not inuse, and it may be moved readily from place to place.

Although a preferred form of rowing machine has been described in theforegoing, certain aspects of this invention are not limited to theparticular details of apparatus set forth as an example, and it iscontemplated that various and other modifications and applications ofthe invention will occur to those skilled in the art. It is thereforintended that the appended claims shall cover such modifications andapplications as do not depart from the true spirit and scope of theinvention.

What is claimed as new and is desired to be secured by Letters Patent ofthe United States is:

1. In a rowing machine of the character having an oar simulating elementwith a hand grip portion at one end and means mounting said oar elementat its other end to swing about a vertical axis to simulate oar strokemovement in one direction and oar return movement in the reversedirection; and to pivot about a horizontal axis to simulate oar dippingposition when said hand grip portion is raised and oar lifting positionwhen lowered, that improvement comprising a closed circuit, fluid-filledhydraulic piping system,

a piston in said system actuated by said oar element for initiatingfluid flow and circulation in said system when said oar hand grip is inoar dipping position and is swung about its said vertical axis in adirection to simulate an oar stroke movement,

fluid driven inertia means in said system sustaining fluid flow andcirculation in said system when once initiated by said piston, saidmeans continuing to apply fluid pressure in said system through saidpiston against said oar element in oar stroke move ment direction whensaid hand grip portion of said oar is in raised oar dipping simulatingposition, and

a bypass in said hydraulic system around said piston,

including a normally closed valve,

means for opening said valve actuated by said oar element when said handgrip portion thereof is in lowered pivoted oar lifting position aboutits horizontal axis, the opening of said valve relieving said oarelement from fluid pressure applied by said inertia means through saidpiston,

whereby when said bypass valve is opened by lowering said hand grip tosimulate oar lifting position said oar element may be swung freely inthe reverse direction about its vertical axis as when simulating oarreturn movement.

2. In a rowing machine of the character having an elongated oarsimulating element with a hand grip portion at one end and meansmounting said oar element at its other end to swing about a verticalaxis to simulate oar stroke movement in one direction and oar returnmovement in the reverse direction; and to rotate about its ownlongitudinal axis substantially 90 from a normal blade position tosimulate blade feathering position when said hand grip is twisted, thatimprovement comprising a closed circuit, fluid-filled hydraulic pipingsystem,

a piston in said system actuated by said oar element for initiatingfluid flow and circulation in said system when said oar hand grip is innormal blade position and is swung about its said vertical axis in adirection to simulate an oar stroke movement,

fluid driven inertia means in said system sustaining fluid flow andcirculation in said system when once initiated by said piston, saidmeans continuing to apply fluid pressure in said system through saidpiston against said oar element in oar stroke movement direction whensaid hand grip portion of said oar is in normal blade position,

a bypass in said hydraulic system around said piston,

including a normally closed valve,

means for opening said valve actuated by said oar element when said handgrip portion thereof is twisted about its own axis and rotated to bladefeathering position at 90 from normal, the opening of said valverelieving said oar element from fluid pressure applied by said inertiameans through said piston,

whereby when said bypass valve is opened by rotating said hand grip toblade feathering position said oar element may be swung freely in thereverse direction about its vertical axis as when simulating oar returnmovement.

3. In a rowing machine of the character having an elongated oarsimulating element with a hand grip portion at one end and meansmounting said oar element at its other end to swing about a verticalaxis to simulate oar stroke movement in one direction and oar returnmovement in the reverse direction; to pivot about a horizontal axis tosimulate oar dipping position when said hand grip portion is raised andoar lifting position when lowered; and to rotate about its ownlongitudinal axis substantially 90 from a normal blade position tosimulate a blade feathering position when said hand grip is twisted,that improvement comprising a closed circuit, fluid-filled hydraulicpiping system,

a piston in said system actuated by said oar element for initiatingfluid flow and circulation in said system when said oar hand grip is innormal blade and oar dipping positions and is swung about its verticalaxis in a direction to simulate an oar stroke movement,

fluid driven inertia means in said system sustaining fluid flow andcirculation in said system when once initiated by said piston, saidmeans continuing to apply fluid pressure in said system through saidpiston against said oar element in oar stroke movement direction whensaid hand grip portion of said oar is in raised, oar dipping simulatingposition and in normal blade position,

a bypass in said hydraulic system around said piston,

including a normally closed valve,

means for opening said valve actuated by said oar element when said handgrip portion thereof is in lowered pivoted oar lifting position aboutits horizontal pivot axis, and

means for opening said valve actuated by said oar element when said handgrip portion thereof is twisted about its own axis and rotated to bladefeathering position at from normal,

the opening of said valve by either means relieving said oar elementfrom fluid pressure applied by said inertia means through said piston,

whereby when said bypass valve is opened by lowering said hand grip tosimulate oar lifting position or by rotating said hand grip to bladefeathering position, said oar element may be swung freely in the reversedirection about its vertical axis as when simulating oar returnmovement.

4. In a rowing machine of the type having a frame and a pair of oarsimulating elements mounted pivotally with respect thereto at each sideto swing back and forth about vertical axes at their outer ends, thatimprovement comprising a pair of piston members each movable back andforth with a said oar element as said oar element swings about itsvertical axis,

a cooperating piston chamber for each said piston member, in whichchamber said member is movable back and forth,

a fluid filled hydraulic piping system comprising a pair of closed loopsextending symmetrically on either side of said frame,

each said loop including a said piston chamber at its outer end, eachsaid chamber being connected in its said loop by fluid openings oneither side of its respective piston member,

a hydraulic motor-pump device centrally included in said piping system,

a fluid inlet connection and a fluid outlet connection on said device,each connection being common to both said loops of said system, saiddevice being driven as a motor by passage of fluid therethrough from asaid piston to said inlet and a flywheel driven by said motor-pumpdevice upon passage of fluid through said device and driving said deviceas a pump to circulate fluid from said common outlet through both loopsof said system toward both said piston chambers and the pistons therein.

5. In a rowing machine of the type having a frame and a pair of oarsimulating elements mounted pivotally with respect thereto at each sideto swing back and forth about axes at their outer ends, that improvementcomprismg a fluid filled hydraulic piping system comprising a pair ofclosed loops extending on either side of said frame,

a piston receiving chamber at each side of said frame, each chamberhaving spaced openings therein for the passage of fluid,

a cooperating swinging piston member in each chamber movable back andforth between said spaced openings in said chamber as a said oar elementswings about its axis,

a rotary hydraulic motor-pump device having a fluid inlet and a fluidoutlet, said device being driven by passage of fluid therethrough fromsaid inlet to said outlet,

each of said loops including a first section leading from a said openingin a piston chamber to said motor- 9 10 pump fluid inlet, and a secondsection leading from mechanisms for opening said valve means andbypasssaid fluid outlet to the other said opening in said ing a saidpiston in a loop of said piping system, piston chamber, actuated by asaid oar element when said element whereby said fluid inlet and saidfluid outlet on said hand grip portion is positioned to simulate oarliftmotor-pump device are common to both said loops 5 ing andfeathering. of said system, and each said piston chamber is con- 7. Animproved rowing machine according to claim 6, nected in a said loop ofsaid system, and additionally comprising a flywheel mtatably driven ySaid -P p device a pipe section connecting together portions of the saidupon passage of fluid from one said opening in a loops in Said i iSystem and Pistol} chamber through a Said Section in a loop 10 fluidpressure indicating instruments connected in said of said system to saidcommon inlet and through pipe sectimL f l ineriia of said w whsll form8. An improved rowing machine according to claim 6, mg, driving saiddevice to pump fluid from said comadditionally comprising 2223 3 2 a? ggg gg zl ifi ag i ia: 15 speed and distance indicators driven by saidfluid driven p y inertia means.

other said spaced opening in both said piston charnhers and the Swingingpiston members therein. 9. An improved rowing machine according to claim6,

6. In a rowing machine of the character having a pair addmonanycompflsnlg of oar simulating elements with hand grip portions at apsrfomlancej mdlcator mechamcany dl'lven by sald their inner ends andmeans mounting said oar elements 0 fluid driven mama mfians, at theirouter ends to swing about axes to simulate oar 3 P p SectiQn Common toeach 0f the 100198 of Said stroke movement and oar lifting andfeathering positions, double loop hydraulic system, and that improvementcomprising a hydraulic pressure indicator driven by fluid in said aclosed double loop, fluid-filled hydraulic piping syspipe section.

tem, w a piston in each loop of said system actuated by a ReferencesCited by the Examiner said oar element for initiating fluid flow andcirculation in said loop when said oar element is swung UNITED STATESPATENTS about its said axis to simulate an oar troke move- 445,7263/1891 Coop 272-72 ment, 30 927,833 7/ 1909 Cunningham 27272 fluiddriven inertia means in said system common to 1,598,940 9/1926 Smith27272 both said loops sustaining fluid floW and circulation in FOREIGNPATENTS said system when once initiated by a said piston,

said means normally continuing to apply fluid pres- 393,319 3/1924Germany.

sure in both loops of said system through said pis- 781,612 8/1957 GreatBritain.

tons against said oar elements in oar stroke movemem direction RICHARDC. PINKHAM, Primary Examiner. normally closed valve means in each saidloop by- A, W, KRAMER, Assistant Examiners.

passing the respective pistons in the loops, and

6. IN A ROWING MACHINE OF THE CHARACTER HAVING A PAIR OF OAR SIMULATINGELEMENTS WITH HAND GRIP PORTIONS AT THEIR INNER ENDS AND MEANS MOUNTINGSAID OAR ELEMENTS AT THEIR OUTER ENDS TO SWING ABOUT AXES TO SIMULATEOAR STROKE MOVEMENT AND OAR LIFTING AND FEATHERING POSITIONS, THATIMPROVEMENT COMPRISING A CLOSED DOUBLE LOOP, FLUID-FILLED HYDRAULICPIPING SYSTEM, A PISTON IN EACH LOOP OF SAID SYSTEM ACTUATED BY A SAIDOAR ELEMENT FOR INITIATING FLUID FLOW AND CIRCULATION IN SAID LOOP WHENSAID OAR ELEMENT IS SWUNG ABOUT ITS SAID AXIS TO SIMULATE AN OAR STROKEMOVEMENT, FLUID DRIVEN INERTIA MEANS IN SAID SYSTEM COMMON TO BOTH SAIDLOOPS SUSTAINING FLUID FLOW AND CIRCULATION IN SAID SYSTEM WHEN ONCEINITIATED BY A SAID PISTON, SAID MEANS NORMALLY CONTINUING TO APPLYFLUID PRESSURE IN BOTH LOOPS OF SAID SYSTEM THROUGH SAID PISTONS AGAINSTSAID OAR ELEMENTS IN OAR STROKE MOVEMENT DIRECTION, NORMALLY CLOSEDVALVE MEANS IN EACH SAID LOOP BYPASSING THE RESPECTIVE PISTONS IN THELOOPS, AND MECHANISMS FOR OPENING SAID VALVE MEANS AND BYPASSING A SAIDPISTON IN A LOOP OF SAID PIPING SYSTEM, ACTUATED BY A SAID OAR ELEMENTWHEN SAID ELEMENT HAND GRIP PORTION IS POSITIONED TO SIMULATE OARLIFTING AND FEATHERING.